"PHP is all about creating dynamic web-sites with the least fuss
and the most fun. To create these websites we need to use databases
to retrieve login information, to splash dynamic news onto the web
page and store forum postings. So let's say we were using the
popular MySQL database for this. Your company has done such a
fantastic job that the Web site is more popular than your wildest
dreams. You find that MySQL cannot scale to handle the workload;
time to switch databases."
"Unfortunately in PHP every database is accessed slightly
differently. To connect to MySQL, you would use mysql_connect();
when you decide to upgrade to Oracle or Microsoft SQL Server, you
would use ocilogon() or mssql_connect() respectively. What is worse
is that the parameters you use for the different connect functions
are different also.. One database says po-tato, the other database
says pota-to. Oh-oh."
"A database wrapper library such as ADODB comes in handy
when you need to ensure portability. It provides you with a common
API to communicate with any supported database so you don't have to
call things off."